using System;

public class Exercise5

{

    public static void Main()

    {

        Console.WriteLine("\nBy Erick de la Rosa");

        double r,per_cir;

        double PI = 3.14;

        Console.WriteLine("\nInput the radius of the circle : ");

        r = Convert.ToDouble(Console.ReadLine());

        per_cir = 2 * PI * r;

        Console.WriteLine("Perimeter of Circle : {0}", per_cir);

        Console.ReadLine();

    }

}